Bandwidth is a term that describes the rate at which data can be transmitted across a network path connecting one or more computers. The faster data is exchanged between computers or other nodes, the higher the bandwidth is said to be for that connection. Conversely, the slower data is exchanged, the lower the bandwidth is said to be for that connection. Thus, bandwidth relates to the amount of data exchanged over the network by a computer or node over time.
Typical network systems such as local area networks (LANs) or wide area networks (WANs) are limited to only a certain amount of bandwidth that is available for use by one or more computers or nodes that comprise the system. To accommodate the varying requirements of the network bandwidth users (e.g., any entity requiring bandwidth), the available bandwidth must be effectively apportioned among the users, while as much as possible, maintaining acceptable performance for the entire network system. Bandwidth allocation is the process of distributing the available bandwidth within a network system amongst one or more users.
One of the most widely used bandwidth allocation techniques involves segmenting a total available bandwidth into equal blocks, and assigning a block of bandwidth to each user within the system. The assigned block indicates the rate at which each computer within the system may transmit data to another computer across the network. Typically, an access server or access point that manages bandwidth resources within the network system performs this assignment or allocation technique. By segmenting the bandwidth, each connected computer is assigned a certain fixed amount of bandwidth for which to perform its particular network tasks. For example, if the network system makes 1 Mbps (megabits per second) of bandwidth available to perform a specific function, and there are ten connected computers, each connected computer is assigned a 100 Kbps (kilobits per second) block of bandwidth (1 Mbps available bandwidth divided by 10 computers). However, this technique has limited effectiveness as it can result in significant under utilization of bandwidth. Not every computer may actually use all of its 100 Kbps of assigned bandwidth, such as due to other network bottlenecks (e.g., a slow link in the Internet or heavy Internet traffic) or constraints in the computer or application itself that impede the rate at which data may be transmitted from the computer and across the network. As a result, more bandwidth ends up being reserved than is actually used, preventing the unused bandwidth from being put to better use. Likewise, a computer that needs more than the allotted amount will be prevented from gaining access to the required bandwidth.
Another bandwidth allocation technique in use today involves segmenting available bandwidth across an entire network path between one or more computers. This bandwidth allocation technique is based on the premise that if the bandwidth is distributed equitably across the entire path, then no under utilization (over assignment) of bandwidth can occur and optimal performance is achieved. As an example of this technique, consider a first computer tied to a first network system, and a second computer tied to a second network system that communicates with the first network system via the Internet. The network path between the two computers includes the various computing devices within each respective network system (e.g., access servers, routers, proxies) as well as potentially a multitude of computing devices within the Internet itself. The bandwidth allocation technique would, in this scenario, require calculating the available bandwidth of the entire network path between the first and second computer, and then assigning blocks of bandwidth accordingly. While this technique can prove effective, it requires a significant amount of state information to be constantly maintained and transferred by each of the computing devices to one another in order to account for constantly changing network conditions. As a result, the amount of traffic placed on the network in sharing this information degrades the performance of the network, and thus limits the available bandwidth across the network path. Moreover, if the path between the first and second computers includes one or more computing devices that are not able to generate or interpret state information, this bandwidth allocation technique is rendered useless.